Fully documented source code for Teletext Elite

BBC Micro cassette Elite | BBC Micro disc Elite | 6502 Second Processor Elite | BBC Master Elite | Acorn Electron Elite | Commodore 64 Elite | Apple II Elite | NES Elite | Elite-A | Teletext Elite | Elite Universe Editor | Elite Compendium (BBC Master) | Elite Compendium (BBC Micro) | Elite over Econet | Flicker-free Commodore 64 Elite | BBC Micro Aviator | BBC Micro Revs | Archimedes Lander

This repository contains source code for Teletext Elite on the BBC Micro and BBC Master 128.

Teletext Elite is the full version of BBC Micro disc Elite, but all graphics have been converted to use the BBC's teletext mode 7. For more information, see the elite.bbcelite.com website.

This repository contains the full source code for Teletext Elite, which you can build yourself on a modern computer. See below for more details on browsing the source code and building Teletext Elite from the source.

Contents

• Acknowledgements

  • A note on licences, copyright etc.

• Browsing the source in an IDE

• Folder structure

• Elite Compendium

• Building Teletext Elite from the source

  • Requirements
  • Windows
  • Mac and Linux
  • Build options
  • Verifying the output
  • Log files
  • Auto-deploying to the b2 emulator

Acknowledgements

Elite was written by Ian Bell and David Braben and is copyright © Acornsoft 1984.

The code on this site has been reconstructed from a disassembly of the version released on Ian Bell's personal website.

The commentary and Teletext conversion code are copyright © Mark Moxon. Any misunderstandings or mistakes in the documentation are entirely my fault.

The Teletext routines are by Kieran Connell and Simon Morris of the Bitshifters, and were adapted from Bresenham routines by Rich Talbot-Watkins. See the Bitshifters teletextr repository for the original code.

Huge thanks are due to the original authors for not only creating such an important piece of my childhood, but also for releasing the source code for us to play with; to Paul Brink for his annotated disassembly; and to Kieran Connell for his BeebAsm version, which I forked as the original basis for this project. You can find more information about this project in the accompanying website's project page.

Thanks to the Bitshifters for their help in building the musical version of BBC Micro Elite, and in particular Kieran Connell, Simon Morris and Negative Charge for the music player and ported music files. Thanks also to Tricky and J.G.Harston for their sideways RAM utilities.

The following archive from Ian Bell's personal website forms the basis for this project:

• BBC Elite, disc version

A note on licences, copyright etc.

This repository is not provided with a licence, and there is intentionally no LICENSE file provided.

According to GitHub's licensing documentation, this means that "the default copyright laws apply, meaning that you retain all rights to your source code and no one may reproduce, distribute, or create derivative works from your work".

The reason for this is that Teletext Elite is intertwined with the original Elite source code, and the original source code is copyright. The whole site is therefore covered by default copyright law, to ensure that this copyright is respected.

Under GitHub's rules, you have the right to read and fork this repository... but that's it. No other use is permitted, I'm afraid.

My hope is that the educational and non-profit intentions of this repository will enable it to stay hosted and available, but the original copyright holders do have the right to ask for it to be taken down, in which case I will comply without hesitation. I do hope, though, that along with the various other disassemblies and commentaries of this source, it will remain viable.

Browsing the source in an IDE

If you want to browse the source in an IDE, you might find the following useful.

• The most interesting files are in the main-sources folder:

  • The main game's source code is in the elite-source-flight.asm and elite-source-docked.asm files (for when we're in-flight or docked) - this is the motherlode and probably contains all the stuff you're interested in.

  • The game's loader is in the elite-loader1.asm, elite-loader2.asm and elite-loader3.asm files - these are mainly concerned with setup and copy protection. The last file contains the source for the Saturn loading screen.

  • The following source files contain Teletext-specific routines and macros, and are included in the main source files as required: elite-teletext-docked.asm, elite-teletext-flight.asm, elite-teletext-lines.asm, elite-teletext-macros.asm, elite-teletext-sixels.asm and elite-teletext-text.asm

• It's probably worth skimming through the notes on terminology and notations on the accompanying website, as this explains a number of terms used in the commentary, without which it might be a bit tricky to follow at times (in particular, you should understand the terminology I use for multi-byte numbers).

• The annotated source files contain both the original Acornsoft code and all of the modifications made to convert the original into Teletext Elite, so you can look through the source to see exactly what's changed in order to convert it to mode 7. Any code that I've removed from the original version is commented out in the source files, so when they are assembled they produce the Teletext Elite binaries, while still containing details of all the modifications. You can find all the diffs by searching the sources for Mod:.

• Teletext Elite incorporates the flicker-free algorithm from BBC Master Elite, which reduces the amount of flicker in the ship-drawing routines, and it also includes flicker-free planet-drawing routines. For more information on flicker-free Elite, see the hacks section of the accompanying website.

• There are loads of routines and variables in Elite - literally hundreds. You can find them in the source files by searching for the following: Type: Subroutine, Type: Variable, Type: Workspace and Type: Macro.

• If you know the name of a routine, you can find it by searching for Name: <name>, as in Name: SCAN (for the 3D scanner routine) or Name: LL9 (for the ship-drawing routine).

• The source code is designed to be read at an 80-column width and with a monospaced font, just like in the good old days.

I hope you enjoy exploring the inner workings of Teletext Elite as much as I've enjoyed writing it.

Folder structure

There are three main folders in this repository, which reflect the order of the build process.

• 1-source-files contains all the different source files, such as the main assembler source files, image binaries, fonts, boot files and so on.

• 2-build-files contains build-related scripts, such as the checksum and encryption script.

• 3-assembled-output contains the output from the assembly process, when the source files are assembled and the results processed by the build files.

• 4-reference-binaries contains the correct binaries for the game, so we can verify that our assembled output matches the reference.

The source files in the first folder are heavily based on the repositories containing the fully documented source code for the disc version of Elite on the BBC Micro.

Elite Compendium

This repository also includes a version of Teletext Elite for the Elite Compendium, which incorporates all the available hacks in one game. The Compendium version is in a separate branch called elite-compendium, which is included in the Elite Compendium repository as a submodule.

The annotated source files in the elite-compendium branch contain both the original Acornsoft code and all of the modifications for the Elite Compendium, so you can look through the source to see exactly what's changed. Any code that I've removed from the original version is commented out in the source files, so when they are assembled they produce the Compendium binaries, while still containing details of all the modifications. You can find all the diffs by searching the sources for Mod:.

For more information on the Elite Compendium, see the hacks section of the accompanying website.

Building Teletext Elite from the source

Builds are supported for both Windows and Mac/Linux systems. In all cases the build process is defined in the Makefile provided.

Requirements

You will need the following to build Teletext Elite from the source:

• BeebAsm, which can be downloaded from the BeebAsm repository. Mac and Linux users will have to build their own executable with make code, while Windows users can just download the beebasm.exe file.

• Python. The build process has only been tested on 3.x, but 2.7 might work.

• Mac and Linux users may need to install make if it isn't already present (for Windows users, make.exe is included in this repository).

For details of how the build process works, see the build documentation on bbcelite.com.

Let's look at how to build Teletext Elite from the source.

Windows

For Windows users, there is a batch file called make.bat which you can use to build the game. Before this will work, you should edit the batch file and change the values of the BEEBASM and PYTHON variables to point to the locations of your beebasm.exe and python.exe executables. You also need to change directory to the repository folder (i.e. the same folder as make.bat).

All being well, entering the following into a command window:

make.bat

will produce a file called teletext-elite.ssd in the project folder that contains Teletext Elite, which you can then load into an emulator, or into a real BBC Micro using a device like a Gotek.

Mac and Linux

The build process uses a standard GNU Makefile, so you just need to install make if your system doesn't already have it. If BeebAsm or Python are not on your path, then you can either fix this, or you can edit the Makefile and change the BEEBASM and PYTHON variables in the first two lines to point to their locations. You also need to change directory to the repository folder (i.e. the same folder as Makefile).

All being well, entering the following into a terminal window:

make

will produce a file called teletext-elite.ssd in the project folder that contains Teletext Elite, which you can then load into an emulator, or into a real BBC Micro using a device like a Gotek.

Build options

By default the build process will create a typical Elite game disc with a standard commander. There is one argument you can pass to the build to change how it works. It is:

• commander=max - Start with a maxed-out commander (specifically, this is the test commander file from the original source, which is almost but not quite maxed-out)

• verify=no - Disable crc32 verification of the game binaries

So, for example:

make commander=max

will build Teletext Elite with a maxed-out commander.

See below for more on the verification process.

Verifying the output

The default build process prints out checksums of all the generated files, along with the checksums of the files from the original sources. You can disable verification by passing verify=no to the build.

The Python script crc32.py in the 2-build-files folder does the actual verification, and shows the checksums and file sizes of both sets of files, alongside each other, and with a Match column that flags any discrepancies.

The binaries in the 4-reference-binaries folder are the game binaries for the released game, while those in the 3-assembled-output folder are produced by the build process. For example, if you don't make any changes to the code and build the project with make, then this is the output of the verification process:

Results for variant: sth
[--originals--]  [---output----]
Checksum   Size  Checksum   Size  Match  Filename
-----------------------------------------------------------
352aba53  21889  352aba53  21889   Yes   D.CODE.bin
9b17e59d  21889  9b17e59d  21889   Yes   D.CODE.unprot.bin
c55ab2f5   2560  c55ab2f5   2560   Yes   D.MOA.bin
83fb82f1   2560  83fb82f1   2560   Yes   D.MOB.bin
c9ee981b   2560  c9ee981b   2560   Yes   D.MOC.bin
3ef85dbc   2560  3ef85dbc   2560   Yes   D.MOD.bin
dabf09f1   2560  dabf09f1   2560   Yes   D.MOE.bin
e27f5708   2560  e27f5708   2560   Yes   D.MOF.bin
28e9201c   2560  28e9201c   2560   Yes   D.MOG.bin
73a67889   2560  73a67889   2560   Yes   D.MOH.bin
54fa021d   2560  54fa021d   2560   Yes   D.MOI.bin
2301ae15   2560  2301ae15   2560   Yes   D.MOJ.bin
df0dce97   2560  df0dce97   2560   Yes   D.MOK.bin
6a3553d0   2560  6a3553d0   2560   Yes   D.MOL.bin
8cd0a690   2560  8cd0a690   2560   Yes   D.MOM.bin
332057cf   2560  332057cf   2560   Yes   D.MON.bin
19da6bcf   2560  19da6bcf   2560   Yes   D.MOO.bin
f60de1ba   2560  f60de1ba   2560   Yes   D.MOP.bin
c73d535a    256  c73d535a    256   Yes   ELITE2.bin
17eefeec   2816  17eefeec   2816   Yes   ELITE3.bin
166691a9   5104  166691a9   5104   Yes   ELITE4.bin
02d83bdb   5104  02d83bdb   5104   Yes   ELITE4.unprot.bin
0f9e270b    256  0f9e270b    256   Yes   MISSILE.bin
fbf74546    883  fbf74546    883   Yes   MNUCODE.bin
98b4ea88  21491  98b4ea88  21491   Yes   T.CODE.bin
932c3ba3  21491  932c3ba3  21491   Yes   T.CODE.unprot.bin
11768233   1024  11768233   1024   Yes   WORDS.bin

All the compiled binaries match the originals, so we know we are producing the same final game as the released variant.

Log files

During compilation, details of every step are output in a file called compile.txt in the 3-assembled-output folder. If you have problems, it might come in handy, and it's a great reference if you need to know the addresses of labels and variables for debugging (or just snooping around).

Auto-deploying to the b2 emulator

For users of the excellent b2 emulator, you can include the build parameter b2 to automatically load and boot the assembled disc image in b2. The b2 emulator must be running for this to work.

For example, to build, verify and load the game into b2, you can do this on Windows:

make.bat all b2

or this on Mac/Linux:

make all b2

If you omit the all target then b2 will start up with the results of the last successful build.

Note that you should manually choose the correct platform in b2 (I intentionally haven't automated this part to make it easier to test across multiple platforms).

---

Right on, Commanders!

Mark Moxon